Studies are proposed to continue physiological and biochemical investigations of vertebrate insecticide resistance. The method is to study organ, cellular and subcellular resistant and susceptible fish responses to in vivo and in vitro insecticide treatments. The objectives are: 1) to determine insecticide uptake rates and binding capacities in resistant and susceptible fish; 2) to study resistant cellular response when two insecticides are present; 3) to study biochemical and physiological differences in resistant fish membrane systems; 4) to study mitochondrial and microsomal enzymes; 5) to investigate possible herbicide resistance; 6) to study hormones and enzyme levels in relation to insecticide effects; 7) to broaden our present studies on Gambusia affinis (mosquitofish) to include other resistant fish populations, such as, Notemigonus crysoleucas (golden shiner) and Lepomis cyanellus (green sunfish).